Series-parallel Cage Tap-changer

Series-Parallel Cage Tap-Changer A padmount or pad-mounted transformer is a ground mounted electric power distribution transformer in a locked steel cabinet mounted on a concrete pad. Since all energized connection points are securely enclosed in a grounded metal housing, a padmount transformer...

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Series-Parallel Cage Tap-ChangerA padmount or pad-mounted transformer is a ground mounted electric power distribution transformer in a locked steel cabinet mounted on a concrete pad. Since all energized connection points are securely enclosed in a grounded metal housing, a padmount transformer can be installed in places that do not have room for a fenced enclosure. Padmount transformers are used with underground electric power distribution lines at service drops, to step down the primary voltage on the line to the lower secondary voltage supplied to utility customers. A single transformer may serve one large building, or many homes.

Pad-mounted transformers are made in power ratings from around 75 to around 5000 kVA and often include built-in fuses and switches. Primary power cables may be connected with elbow connectors, which can be operated when energized using a hot stick and allows for flexibility in repair and maintenance.

The frequency of maintenance to tap changers is dependent on the condition of the diverter switch and the necessity to maintain the motor drive unit. Maintenance of the diverter switch should be carried out on a cyclic basis, but on transformers where frequency of tap change is high, maintenance may be necessary before the cyclic maintenance becomes due. A certain period should not be exceeded between inspections. When considering inspection periods, serious consideration should be given to the breaking of circulating current which in some cases may exceed the load current.